Cannot launch a VM after configuring Shared File Systesm (NFS): No valid host was found. There are not enough hosts available.

I have a controller and two compute nodes in my OpenStack environment. I could successfully run and launch a VM.

I wanted to configure Live Migration, so I installed NFS on controller and shared /var/lib/nova/instances and mount it on compute nodes. I also give read/write permission to nova user for the shared folder.

The problem is, now I cannot launch a VM. It gives the error: No valid host was found. There are not enough hosts available.

This is the nova-compute error log on compute node 1: http://paste.openstack.org/show/594537/

It applears that the problem is from the permissions! But I don't know how to fix it.